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The Anticipation of Gravity in Human Ballistic Movement

  • Stretch-shortening type actions are characterized by lengthening of the pre-activated muscle-tendon unit (MTU) in the eccentric phase immediately followed by muscle shortening. Under 1 g, pre-activity before and muscle activity after ground contact, scale muscle stiffness, which is crucial for the recoil properties of the MTU in the subsequent push-off. This study aimed to examine the neuro-mechanical coupling of the stretch-shortening cycle in response to gravity levels ranging from 0.1 to 2 g. During parabolic flights, 17 subjects performed drop jumps while electromyography (EMG) of the lower limb muscles was combined with ultrasound images of the gastrocnemius medialis, 2D kinematics and kinetics to depict changes in energy management and performance. Neuro-mechanical coupling in 1 g was characterized by high magnitudes of pre-activity and eccentric muscle activity allowing an isometric muscle behavior during ground contact. EMG during pre-activity and the concentric phase systematically increased from 0.1 to 1 g. Below 1 g the EMG in the eccentric phase was diminished, leading to muscle lengthening and reduced MTU stretches. Kinetic energy at take-off and performance were decreased compared to 1 g. Above 1 g, reduced EMG in the eccentric phase was accompanied by large MTU and muscle stretch, increased joint flexion amplitudes, energy loss and reduced performance. The energy outcome function established by linear mixed model reveals that the central nervous system regulates the extensor muscles phase- and load-specifically. In conclusion, neuro-mechanical coupling appears to be optimized in 1 g. Below 1 g, the energy outcome is compromised by reduced muscle stiffness. Above 1 g, loading progressively induces muscle lengthening, thus facilitating energy dissipation.

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Metadaten
Author:Janice Waldvogel, Ramona Ritzmann, Kathrin Freyler, Michael Helm, Elena Monti, Kirsten AlbrachtORCiD, Benjamin StäudleORCiD, Albert Gollhofer, Marco Narici
DOI:https://doi.org/10.3389/fphys.2021.614060
ISSN:1664-042X
Parent Title (English):Frontiers in Physiology
Publisher:Frontiers
Place of publication:Lausanne
Document Type:Article
Language:English
Year of Completion:2021
Date of the Publication (Server):2021/04/15
Link:https://doi.org/10.3389/fphys.2021.614060
Zugriffsart:weltweit
Institutes:FH Aachen / Fachbereich Medizintechnik und Technomathematik
FH Aachen / IfB - Institut für Bioengineering
collections:Verlag / Frontiers
Open Access / Gold
Licence (German):License LogoCreative Commons - Namensnennung